Moho depth and three-dimensionalPandSstructure of the crust and uppermost mantle in the Eastern Mediterranean and Middle East derived from tomographic inversion of local ISC data

Abstract

SUMMARY ∼82 000 P and S arrival times from ∼3000 sources recorded by ∼250 seismic stations from the revised ISC catalogue are employed to study a circular area of 6 ◦ radius centred on the Dead Sea. We use the linearized tomographic approach based on the rays constructed in a 1-D spherical velocity model and corrected for the Moho depth variation and relief. All the sources were relocated. As the result of simultaneous iterative inversion we get 3-D P and S velocity anomalies in the crust and uppermost mantle, Moho depth and corrected source parameters. The resulting images fit well with the existing tectonic elements in the study area. In the crust, a narrow P and S low-velocity anomaly marks the position of the Dead Sea Transform (DST) that is interpreted as sediments in the shallower layer and a zone of fractured and deformed rocks in the middle and lower crust. There is a narrow (50 km wide) band of thickening of the crust along the DST in the Arava valley between the Red Sea and Dead Sea and some 100 km north of the Dead Sea. This zone may be associated with the minimum of the lithospheric strength and, therefore, explain the location of the DST in the Arava Valley. The velocity anomalies under the crust and the map of the Moho depth clearly distinguish the oceanic (Levant basin) and continental types of crust (Asia Minor, Zagros, Cyprus and Eratosthenes Mount). Verification of the results takes an important part in this study. Inversions of different starting models and independent processing of data subsets show high robustness of the results. Synthetic tests clearly show the limits of the resolving power of the inversion with the existing data set.